PHILADELPHIA  Left-hander Robbie Erlin will undergo a second MRI on his sore throwing elbow Friday in San Diego. The Padres hope the scan, which comes three weeks after an initial MRI, will confirm Erlin has progressed to the point that he can resume throwing in the near future.

“I don’t know that it’s being extra-cautious,” Padres manager Bud Black said, “but it’s going through the process to make sure the doctors are seeing the progress they want to see. They can review each scan and feel pretty good that he’s healing, and, if medically they feel comfortable, then he can start throwing.”

After an MRI revealed fluid in his elbow, Erlin went on the 15-day disabled list May 22, retroactive to May 18. Erlin said he had felt pain in his throwing motion following each of his last three starts.

Before the Padres departed San Diego for their current road trip, Erlin said the symptoms had largely subsided. He was most recently examined by team doctors over the weekend.

“He’s still experiencing a little bit of pain, but it’s lessened,” Black said.

In nine appearances, including eight starts this season, Erlin has gone 3-4 with a 4.53 ERA.

With the 23-year-old remaining on the DL, the Padres will need to continue filling their fifth rotation spot as they go. Black has yet to announce a starter for Saturday’s game against the Mets, though the Padres will choose from Triple-A El Paso right-handers Donn Roach and Odrisamer Despaigne and Double-A San Antonio right-hander Jesse Hahn.

Gettys agrees

The Padres and second-round draft pick Michael Gettys have agreed on a $1.3 million signing bonus, pending a physical. They have also signed outfielder Yale Rosen (11th round), left-hander Danny Wissmann (22nd round) and infielder Mitch Morales (29th round).

Gettys, an outfielder out of Gainesville High (Ga.), was taken with the 51st selection, which comes with a slot value of $1,083,400. The Padres have $6,098,600 to spend on their selections in the top 10 rounds and on the portion of any signing bonus thereafter that exceeds $100,000.

Clubs that spend beyond their allotted pool will pay a high tax on the overage. Depending on how much they go over, teams could also lose draft picks.

As of Thursday afternoon, the Padres remained close to reaching agreements with their first- and third-round selections. The 13th overall pick, North Carolina State shortstop Trea Turner, has a slot value of $2,723,300. The 86th pick, Rice University right-hander Zech Lemond, is valued at $631,900.

Notable

Through 66 games, the Padres are averaging 3.03 runs, the lowest since the 1972 Angels (2.93), the 1972 Rangers (2.99) and the 1972 Indians (3.03).

Padres manager Bud Black successfully challenged a play in the third inning of Thursday’s game, as an infield single by Philadelphia’s Ben Revere was changed to a sacrifice. Black is 7-for-10 on manager reviews this season. His 70 percent success rate is the fourth-best mark in the majors.